Machine for sharpening disc blades

ABSTRACT

A machine for sharpening disc blades consisting of a base, a lower frame, and an upper frame. The upper frame has a drive motor which drives a vertically disposed shaft with a grinding stone mounted on the lower end. The lower frame has a mandril which extends upwardly toward the grinding stone with its support shaft disposed at an angle with respect to the grinding stone shaft. The angle of the mandril shaft with respect to the grinding stone shaft is variable by an adjustment mechanism and the upper end of the mandril has a clamp for securing disc blades to the mandril. The mandril is rotatably driven by a mandril drive motor mounted on the base. The upper end of the mandril shaft is disposed in a liquid tank so that the disc blade is submerged during the grinding contact, thus eliminating noise and flying chips. Effective sharpening of the disc blades is accomplished by rotating the mandril holding the disc blade more slowly than the grinding wheel is rotated and by varying the angle of contact between the disc blade edge and the grinding stone by adjusting the angle between the mandril shaft and the grinding wheel shaft.

United States Patent Ruble July 29, 1975 MACHINE FOR SHARPENING DISCPrimary ExaminerAl Lawrence Smith B ADES Assistant ExaminerNicholas P.Godici [76] Inventor: Lloyd J. Ruble, 225 S. California, Attorney Agentor Fnvmfivergll Gerard Tulare, [22] Filed: 1971 A machine for sharpeningdisc blades consisting of a [21] Appl 212,482 base, a lower frame. andan upper frame. The upper frame has a drive motor which drlves avertically disi posed shaft with a grinding stone mounted on the [52]U.S. Cl 51/126; 5l/l32; 51/209 R; lower end The lowerv frame h a mandrilwhich 51/266 tends upwardly toward the grinding stone with its sup-Illt. t h ft di d t an angIe respect In h [58] Field of Search 51/132,106 R, 51, 356, grinding stone shaft. The angle of the mandril shaft51/266, 124 L, 124 R, 209 R, 126, 237 R, 225 with respect to thegrinding stone shaft is variable by an adjustment mechanism and theupper end of the [56] References Cited mandril has a clamp for securingdisc blades to the UNITED S S P TS mandril. The mandril is rotatablydriven by a mandril 762,399 6/1904 Goehring et d1v 51/266 x drive P TPPer end of 2,127,071 8/1938 Schmalz 51/51 x the m'flhdtll Shaft 18fdlsposed hqutd tank 9 that 2,401,486 6/1946 Jones 51 106 R the (1186blade IS Submerged during the grlhdihg 2,402,305 6/1946 Sutton" 51/106 Rcontact, thus eliminating noise and flying chips. Effec- 2,450,2309/1948 Bush 51/209 R tive sharpening of the disc blades is accomplishedby 2,528,193 lO/l950 Van Allen 51/51 X rotating the mandril the discmore 2,65l,l49 9/1953 Ferm. 5l/l06 R Slowly than the grinding wheel isrotated and by vary 2,747,339 Schelhng L the angle of Contact betweenthe disc hade ge 513321233 55132? 11253121. fiiilijjjj .JJJ..7.S?J2 andthe gnnning none by nninnnng nn nngln between the mandril shaft and thegrinding wheel shaft.

20 Claims, 10 Drawing Figures PATENTED JUL 2 91975 SHEET PATENTED JUL29I975 SHEU PATENTED JULZQ i975 SHEET MACHINE FOR SHARPENING DISC BLADESBACKGROUND OF INVENTION This invention relates generally to grindingmachines and more particularly to machines for grinding the peripheraledges of concave disc blades.

Circular concave steel blades ganged together to form a disc are usedfor a variety of purposes, including plowing earth for farming andtearing up an asphalt road surface for replacement or repair. Theperipheral edges of the disc blades are sharpened to provide thenecessary cutting action in performance of their work and with usebecome dull and must be resharpened. The disc blades are made ofhardened steel and resharpening, therefore, requires a substantialamount of grinding. Since the disc blades are circular and concave aneffective resharpening job requires that the grinding stone be movedaround the periphery of the blade at varying tangential angles to theblade surface so that the peripheral edge of the blade is givensubstantially the same amount and angle of grinding at each point.Normally, the surface of the grinding wheel first engages the peripheraledge of the blade with the plane of the wheel disposed only at a slightangle to a plane normal to the axis of the disc and as the sharpeningprogresses the grinding wheel surface is moved to a greater angle to thenormal plane as the grinding cut moves outwardly to the outermostperiphery of the blade.

Various machines and equipment have been utilized to perform thisgrinding function. These vary from vertically mounted grinding wheelswith the disc blades mounted on a supporting shaft and held against thewheel surface and at an angle to the wheel by hand, to machines whichsupport the disc and the grinding wheel and bring them together forabrasive contact by moving the disc blade or the grinding wheel or both.

Because of the hot particles chipped away from the blade during grindingin the form of sparks, the heat which the grinding friction generates inthe blade, and the noise produced, it is desirable to hold the blade inwater or some other liquid during grinding.

The equipment heretofore known has not been effective in combining allthese desired features into a grinding machine which can be operated bya single operator efficiently and with satisfactory results.

It is, therefore, a major object of my invention to provide a machinefor grinding disc blades which can be operated by a single operator andwill produce the desired sharpening in a minimum amount of time.

Another object of my invention is to provide a machine for grinding discblades of the type described in which the disc blades are submerged inliquid during the grinding operation to trap hot particles, keep theblade steel cool, and minimize noise.

A further object of my invention is to provide a.ma-: chine of the typedescribed in which the disc is auto matically rotated during thesharpening operation to provide uniform contact between all points onthe blade periphery and the grinding wheel.

Still another object of my invention is to provide a machine of the typedescribed in which the mandril which mounts the disc blade is movableangularly with respect to the surface of the grinding stone to vary thetangential angle of contact between the grinding stone and the bladeedge.

Yet a further object of my invention is to provide a machine of the typedescribed in which the blades can be readily mounted and dismounted fromthe support mandril and the grinding stone can be readily changed.

Still a further object of my invention is to provide a machine of thetype described which is relatively inexpensive to manufacture andrequires a minimum of time and operator skill in use.

These and other objects of my invention will become more readilyapparent from the following detailed description of a preferredembodiment and the accompanying drawings in which:

FIG. 1 is a side elevational view of a preferred embodiment of myinvention;

FIG. 2 is a front elevational view of the machine shown in FIG. 1;

FIG. 3 is a sectional plan view taken on line 33 in FIG. 2;

FIG. 4 is a partial sectional side elevational view taken on line 44 inFIG. 2;

FIG. 5 is a partial sectional view taken on line 55 in FIG. 4;

FIG. 6 is an enlarged partial sectional view taken on line 66 in FIG. 4;

FIG. 7 is an exploded perspective view of the disc blade mountingmechanism in my preferred embodiment;

FIG. 8 is a partial sectional plan view taken on line 88 in FIG.,2 andshowing the grinding wheel and its drive motor;

FIG. 9 is a schematic view of the hydraulic control for the grinderwheel feed mechanism; and

FIG. 10 is a partial sectional view taken on line 10-10 in FIG. 1.

Referring now to the drawings, and particularly FIGS. 1 and 2 thereof,the numeral 10 designates my disc blade grinding machine generally. Themachine 10 has a base 12 witha lower frame 14 extending upwardlytherefrom. The lower frame 14 is generally V- shaped upwardly and has arearwardly, directed structural support portion 16. An upper frame 18 ismounted on the lower frame 14 by a hinge 20 connected to the upper endof the lower frame structural support 16.

The upper frame 18 has a grinding wheel support head 22 on its distalend with respect to the hinge 20. The grinding wheel support head 22 isdisposed generally vertically and has a grinding wheel mounting plate23, movably mounted thereon. The grinding wheel mounting plate 23carries a grinding wheel drive motor 24 on its upper portion and agrinding wheel 26 on its lower portion. The grinding wheel, 26 isconnected to a shaft 28 of the drive motor 24 by means of a coupling 30.Below the coupling 30, the drive shaft 28 passes through a bearinghousing 32 with thrust bearings (not shown) which support the weight ofthe grinding wheel. The grinding wheel mounting plate 23 is secured tothe grinding wheel support head 22 by a pair of mounting plate flanges25 positioned on each side of the grinding wheel mounting plate 23. Themounting plate flanges 25 extend rearwardly, substantially normal to thegrinding wheel mounting plate 23 and overlap support head flanges 27 onthe grinding wheel support head 22. The mounting plate flanges 25 havevertically extending slots 29 which align with holes 31 in the supporthead flanges 27. Bolts 33 are disposed through the slots 29 and holes 31to releasably secure the flanges together. A mounting plate lift frame35 is attached to both sides of the grinding wheel mounting plate 23 andsupport head 22. Ahydraulic mounting'plate adjust" ment cylinder 37 isconnected between the grinding wheel support head 22 and the mountingplate lift frame 35 and, upon actuation, moves the grinding wheelmounting plate 23 vertically with respect to the grinding wheel supporthead 22 when the bolts 23 are released to permit movement. Movement ofthe grinding wheel mounting plate 33 with respect to the grinding wheelsupport head 22 adjusts the vertical position of the grinding wheel 26and compensates for wear as more fully explained later. The verticaladjustment position of the grinding wheel is indicated by a scale plate39 mounted on the grinding wheel support head and disposed in indicatingrelationship with a pointer 40 mounted on the grinding wheel mountingplate (see FIGS. 2 and 8).

The grinding wheel 26 consists of a torodial grinding stone 34 mountedin a grinding wheel chuck 36 attached to the lower end of the shaft 28below the bearing housing 32. As best shown in FIG. 6, the grindingwheel chuck 36 has a backing plate 38 connected to the shaft 28 with aperipheral rim 40 projecting normal thereto to provide a cavity 42. 'Anannular retaining ring 44 is secured to the face of the peripheral rim40 by bolts 45, and has a beveled surface 46 on its inner edge whichtapers outwardly and upwardly toward the rim 40. The rim 40 has abeveled surface 47 on its inner edge which tapers outwardly anddownwardly to meet the uppermost end of the surface 46 and form. a wedgeshaped annular slot 48. A wedge shaped split ring 49 is disposed in theslot 48 and has mating surfaces which are engaged by the beveledsurfaces 46 and 47. The beveled surfaces 46 and 47 are so disposed thattightening the bolts 45 to draw the annular. retaining ring 44 towardthe rim 40 forces the split ring 49 radially inward into the cavity 42to engage and grip the periphery of the grinding stone 34. To preventdamage to the grinding stone 34 by this griping action of the split ring49, a gasket 50 is mounted on the periphery of the stone. The gasket 50does not extend to the face of the stone so that it produces nointerference with its grinding function, and further, even if the stoneface is worn to the point where the gasket is exposed to the grindingarea; the gasket merely wears off without effect on the grinding. Theupper bevel 47 is made'very slight to avoid pressing the grinding stoneupward into the chuck when the split ring'49 is driven inwardly.

The torodial grinding stone 34 has an outside diameter substantially thesame as the inside diameter of the peripheral rim 40 on the grindingwheel chuck 36 and end of the mandril in an arcuate direction so thatproper positioning of a disc blade with respect to the;

a thickness substantially greater than the depth of the cavity 42 sothat the grinding stone can be fitted into the cavity and retained thereby the grip ing actionof the jaw members 49, and when so retained thelower portion of the stone will project downwardly therefrom beyond thelowermost portion of the retaining ring 44.

The upper frame 18 is pivotally movable about the hinge 20 by means of ahydraulically operable grinding wheel contact cylinder 52 which isconnected between the upper portion of the lower frame 14 and the distal.portion of the upper frame 18. In its lowermost pivotal position theupper frame rests upon the lower frame and the shaft 28 is positionedsubstantially vertical, disposing the lower surface of the grindingstone ina substantially horizontal plane. 133/ activation of thegrinding wheel control cylinder 52, the upper frame can be moved.pivotally upward from the lower frame, tilting the lower end of thegrinding wheel drive shaft 28 outwardly fromthe lower frame and swingingthe lower surface of the grinding stone so that its plane is angularlyoffset from the horizontal. Swinging the upper frame 18 between itslower and upper positions thereby causes the lower surface of thegrinding stone to trace an arcuate path. H

The pivotal movement of the upper frame 18 with re-' spect to the lowerframe through activation of the grinding wheel control cylinder 52 isachieved by a grinding wheel position control 54 hereafter described ingreater detail.

To protect the operator from injury, the grinding wheel is covered by aband-shaped guard 56 which leaves the lower surface of the grindingstone exposed for engagement with the disc blade. Below the grindingwheel and mounted on the lower frame'14 is a grinding wheel pan 58 intowhich the grinding wheel fitswhen;

the upper frame 18 is in its lowermost position. The grinding wheel pan.58 has a semicircular lower surface which drops off into a tank 60. r

A disc blade support mandril 62 has an upper end 64 which projectsupwardly into the tank 60 and has a lower end 66 which extendsdownwardly outsidethe tank toward the base 12 of the machine. Themandril 62 has a hollow. driveshaft 68 which is rotatably mounted in amandril support housing701by means of 7 an upper end bearing 72 and alower end bearing 74.

The mandril support housing has its upper end mounted in the lower frame14 by means of amounting frame 76 which is secured to the lower frame bya locking stud 78. The locking stud 78 passes through an a cuate slot 80in the lower frame and a vertically disposed linear slot 79 inthemandril upper end 64. Alock I nut 82 is provided'to thread onto thelocking stud=78 and secure the stud in a particularposition in the arcuate slot. The lower end of the mandril support housing i 70 is mountedon the lower frame bymeans of a trun-. ion bearing 84 which permitsmovement of the upper grinding wheel 26 can be achieved, as'laterexplained.

The trunion bearing '84 is mounted on the mandril.

support housing 70 by means of a releasable clamping band 81 secured byabandbolt 83 (see FIG. 10). Since the clamping band'8l is releasable bymeans of the band bolt 83 it isslidable up or down on the mandrilsupport housing 70 to adjust its mounting point. Also,;-

the stub shafts 85 of the trunion bearing 84' are mounted to the lowerfrarne14 by means of bearing caps 87 which are secured to the frame bybearing cap 1 bolts 89. (See FIGS. 1 and 2) The bearing cap bolts 89 4 yare mounted in frame slots 91in the lower frame which are generallyaligned with theaxis of the mandril support housing 70, so that themounting point ofthe stub w shafts 85 in the lower frame 14 is alsoadjustable. The adjustabiiity of the clamping band 81 on the mandrilhousing70 and the stub shafts 85 in the lower frame 14 permitadjustmentiof both the radius and. thecenter point of the arcuatemovement of the upper end 14 of the mandril, as more fully explainedlater.-

The upper end of the mandrilsupport provided about the opening 86 toprevent leakage of liquid from the tank 60. The seal consists of aflanged collar 90 disposed normal to the driveshaft of the mandril andmounted on the upper end of the mandril support housing 70. The collar90 is of sufficient size to overlap the peripheral edges of the opening86 through which the mandril support housing passes and to permitmovement of the mandril support housing in the opening without exposingthe opening for the tank.

To rotate the mandril driveshaft 68, a drive pulley 92 is provided on apower transfer shaft 93 adjacent the lower end of the mandril 62 and isdriven by a mandril drive motor 94 through a drive belt 96 (see FIG. 1).The mandril 62 is, in turn, driven by the power transfer shaft 93through a chain and sprocket drive 97.

To hold a disc blade on the upper end of the mandril 62, a lock shaft 98is provided in the bore of the;man-.

dril driveshaft 68. The lock shaft 98 moves reciprocally in the mandrildriveshaft bore from an extended position in which the upper end of thelockshaft projects upwardly beyond the upper end 64 of the mandril, to aretracted position where the upper end of the lock shaft is withdrawninto the upper end of the mandril. The reciprocal movement of thelockshaft 98 is powered by a hydraulically actuated piston 100 attachedto the lower end of the lockshaft and enclosed by a housing 102. Thepiston 100 is biased by a spring 104 to drive the lockshaft upwardly andis powdered hydraulically to drive the lock shaft downward against thespring bias in a manner well known in the art (see FIG. I).

At the uppermost end of the lockshaft, a sloted head 106 is formed whichcooperates with a lock plate 108 to lock disc blades to the lockshaft.The lock plate 108 has a square center bore 110 which fits over thesquare flange 112 on the sloted head 106 but is locked on the head byone quarter rotation in the slots 114 (see FIG. 7). The slotted head 106is small enough to pass through the bore in a disc blade but the lockplate is 7 larger than the disc blade bore so that when the slotted head106 is moved to its upper position a disc blade may be mounted on thelockshaft by inserting the slotted head through the disc blade bore,setting the lock plate 108 over the slotted head and rotating it onequarter turn to lock it in the slots 114 and then retracting thelockshaft 98 to engage the upper surface of of the blade with the lockplate. To support the lower surface of the disc blade and provide secureclamping of the disc blade to the blade and provide secure clamping ofthe disc blade to the mandril 62,a mandril mounting plate 116 is affixedto the mandril driveshaft 68 at its upper end. The mandril mountingplate 116 projects radially outward from the mandril drive shaft adistance sufficient to provide a secure mounting base for the disc bladebut less than the disc blade diameter to avoid interference with thegrinding of the peripheral edges (see FIG. 4).

The disc blade is thus clamped between the lock plate 108 engaged in theslots 114 on the slotted head 106 on the upper end of the lockshaft andthe periphery of the mandril mounting plate 116 on the upper end of themandril driveshaft, when the lockshaft is driven to its retractedposition by actuation of the piston 100.

To vary the angular dispostion of the axis of mandril 62, a mandrilposition cylinder 118 is provided. The mandril position cylinder 118 ishydraulically actuated and is connected between the lower frame 14 andthe upper end 64 of the mandril, so that extension of the cylinder armdrives the upper end 64 downwardly and retraction draws it upwardlyalong the arc defined by the arcuate slot 80. The locking stud 78 andits locknut 82 releasably secure the mandril upper end 64 in its desiredposition, and the vertically disposed linear slot 79 allows adjustmentof the locking stud 78 in the mandril upper end 64 during its arcuatemovement in slot 80.

The tank 60 is filled with water by means of a water supply system 120.The water supply system 120 includes a reservoir 122, and a water pump124 (see FIG. 2). The reservoir 122 is connected to the tank 60 by meansof a main supply line 126, a return line 128, and an upper supply linewhich branches off of the main supply line and deliverswater underpressure to the grinding wheel pan 58 by means of a nozzle 132.

The nozzle 132 directs water against the lower surface of the grindingstone 34 so that the point of grinding ac- 7 tion is cooled and thegenerated sparks are contained and noise controlled (see FIG. 4). Thewater delivered by the nozzle 132 runs off from the grinding wheel pan58 into the tank 60. A flow control valve 134 is provided in the returnline 128 to control the water. circulation and maintain the water intank 60 at a constant level. Regulation of the flow control valve 134with the capacity of the pump 124 will assure prompt filling andemptying of the tank 60 and will limit the high water level to theheight of the grinding wheel pan 58. To remove any excess water from thegrinding wheel pan 58 an overflow drain 133 is provided.

The grinding Wheel position control 54 consists of a control plunger 136mounted in a cylinder 138 on the upper surface of the lower frame 14(see FIGS. 1 and 9). The plunger 136 is biased to an upper position by aspring 140 in the cylinder 138. The cylinder 138 is filled withhydraulic fluid and has bypass lines 142 which connect the upper portionof the cylinder to its lower portion through a control valve 144. Thecontrol valve 144 permits fluid flow from the lower to the upper portionof cylinder 138 at a controlled rate so that the travel of the plunger136 from its upper position to its lower position in cylinder 138against the bias of spring 140 is restricted in speed. A check valve 146is provided which is a one-way valve and permits free flow of fluid fromthe upper to lower portions of cylinder 138, for free return of thepiston to its upper position. Thus, after the plunger 136 has beendriven to its lower position in the cylinder 138, it can be quicklyreturned to its upper position under the bias of spring 140 as soon asthe driving pressure on the piston is released. The control valve 144 isregulated by a control valve solenoid 148. The solenoid 148 can beelectrically connected with the drive motor 24 so that the feed rate ofthe grinding wheel is controlled by the load on the motor.

The plunger 136 of the grinding wheel position control 54 is engaged bya control foot 150 on the upper frame 16 when the upper frame is loweredinto grinding position by the grinding wheel cylinder 52, and controlsfurther downward movement of the grinding wheel 26. To limit the extentof downward movement of the grinding wheel 26, a limit stop 152 isprovided on the upper surface of the lower frame 14 adjacent thegrinding wheel position control 54. The limit stop 152 consists of alimit stud 154 which is vertically adjustable by threading in a studbase 156 on the lower frame 14, and is engaged by a limit foot 158 onthe upper frame 16.

A limit stop adjustment wheel 160 is provided to readily adjust theposition of the limit stud 154 through a a worm gear (now shown). t

To provide actuation for the hydraulic controls and I actuators, ahydraulic pump 162isprovided on base 12' which is driven by an electricmotor 164- and supplies hydraulic fluid through lines 166. V j

7 To controlthe hydraulic actuators, control valves are also provided ona platform 168 at a convenient posi- 7' ,tion on the machine (see FIG.2). These control valves include a grinding wheel position control;valve 170 which controls the actuation of the grinding wheel positioningcylinder 52, a lockshaft' control valve 172 which controls thereciprocal positioning of the lockshaft 98 through piston 100 incylinder 102,-and a mandril position control valve 174 which controlsthe angular dispostion of the axis of the mandril 62 through mandrilposition cylinder 118. A control valve for the bypass valve control 148and electric switches for controlling the hydraulic pump drive motor164, the water pump 124, the grinding wheel drive motor 2 4, and themanthe mandril housing and the lower frame. When the proper contactangle is established between the lower surface of the grinding stone 34and the peripheral edge of the disc blade to provide the desiredsharpening, the rmandril is locked in thisposition by tightening I I thelock nut 82 on the locking stud 78, and the mandril positioning cylinder118 is deactivated. t

The grinding wheel is then raised again by the grinding wheel'p ositioncontrolvalve 170, and the grinding wheel position control is set forthedesired feed rate. Also, the limit stop 152 is adjustedto the desiredmaxi mum depth of cut.

With the machine drive motor 24, and the mandril drive motor 94, are

and the disc blade o By proper drive connection means the grinding stone7 34 is made to rotate many times faster than the disc dril dri ve motor94, are provided at other appropriate,

jecting through the bore in the center of the disc bladeI During thisinstallation the grinding wheel 26 is swung to' its upper position, awayfrom the point of installa blade so that adequate grinding is providedalong the peripheral edge of the blade.

Next, the grinding wheel is lowered by grinding wheel, i

position control valve 170 into contact withthe peripheral'edge of thedisc blade and the water pump 124isstarted so that the tank 60 is filledand awater spray is t delivered to the point of contact by'the nozzle132. t

As the grinding wheel 26'reaches its lower position,

the control foot 150 on the upper frame 16eng'ages the I plunger 136 ofthe grinding wheel position control 54 i a and the Weight of the'upperframe drives the plunger tion, by pivoting the upper frame 16 upwardlyabout the hinge 20 by actuation of the grinding wheel positioningcylinder 52 (see FIG. 1). The lockshaft 98 of the mandril 62 isreciprocated to its upward position with the slotted head 108 projectingabove the upper downward in the cylinder 138. Since the fluid inthecylinder 138 must transfer from the lower to the upper portion of thecylinder through the control valve 144 in order for the plunger 136 tomove downwardly, the" speed of downward movement of the upper frame,and,

therefore, of the grindingwheehis controlled by the 8 control valve.

end of the mandril, by release of the piston 100 in the cylinder 102 tothe biasing of spring 104. And, the grinding wheel position control 54is reset by raising the grinding'wheel head to permit plungeril36to bedriven to its upper position by the bias spring 140. Also,

though the water pump 124 and the hydraulic pump drive motor 164 are inoperation, the grinding wheel 7 drive motor 24'and the mandril drivemotor 94 are off. I

With the disc blade positioned on the upper end 64 of the mandril 62 andover the slotted head 1060f the lockshaft 98, as described, the blade isbrought to rest on the mandril mounting plate 116. The lock plate 108 isthen placed over the slotted'head 106 and rotated a quarter turn tosecure it in the slots 114. Next, the lock- I shaft control valve isactuated to draw the lockshaft 98 downward by action of hydraulic fluidon the piston 100, and thus clamp the disc blade on the upper end 64 ofthe mandril between the locking plate 108 and the mandril mounting plate116; it 7 With the grinding wheel drive motor 24 still off, the grindingwheel is then lowered into contact position with the disc blade and theangular and axial disposition of the mandril axis adjusted by releasingthe lock nut 82 on locking stud 78 and tilting the mandril upper end 64in the trunion bearing 84 by means of mandril positioning cylinder 118and its control valve 174, and 7 if necessary, by adjusting the positionof thc trunion on When sufficienttime has passed the plunger 136 will ai be driven downward far enough for the limit foot 158 on the upperframe 16 to engage the limit stud 154' and further downward movementwill be'thereby prevented. a At this point, the disc blade edge will andif necessary to achieve the proper sharpening, the

' grinding operation can be recycled with the bladeedge positioned at adifferent angle to the, stone surface by resetting theangulardi'sposition of the mandril axis.

When the desired sharpening is achieved, the disc 7 blade is removedanda new blade applied to' the mandril 62 in the mannerpreviouslydescribed.

It will be understood,of course, that duringthe grinding operation, allof thedisc blade except the small portion at the point of contact withthe stone will be submerged in the water in tank 60, and even'theportion atthe point of contact will be subject to water spray from thenozzle 132., The sparks, noise andheat normally which accompany grindingwill, therefore, be'virtually eliminated.

7 Furthermore, it will be seen that disc without any substantial manualeffortl When the grinding stone 34 becomes sufficiently I I worn tomerit it, a new stone can be applied by merely loosening the bolts whichhold the retaining rirnt44 'of the grinding wheel chuck 36 to releasethe worn stone, inserting a new stone banded with the gasket thus setup, the grinding wheel turned on to commence rotation, of thegrindingstone be inspected blades can be p rapidly applied to andremoved'from:my machine, the I grinding can be carefully controlled as to both rateand angle, and all this c'an be achieved by one operator,

and securing it in the chuck by tightening the bolts 45 3. A machine forsharpening disc blades as described to drive the split ring 49 againstthe gasket. in claim 1, in which:

it will thus be understood that l have provided a masaid mandril meansincludes a mandril having a proxchine for sharpening disc blades whichis fully Capable imal end mounted to said frame and a distal end ofachieving the objects and providing the advantages" 5 disposed adjacentsaid grinding surface with dig heretofore attributed to it. blade clampmeans thereon, said disc blade clamp I claim: means having a lock shaftinterconnected with said l. A machine forsharpening disc bladescomprising: mandril with a Proximal and adjacent the Proximal a f end ofsaid mandril and a'distal end adjacent the distal end of said mandriland disposed for reciprocating axial movement with respect to saidmandril from an extended position with said distal end of said lockshaft extended outwardly from the distal end of said mandril to aretracted position with the distal end of said lock shaft substantiallycoextensive with the distal end of said mandril, and having a disc blademounting plate on the distal end of said mandril, and further includes alock plate releasably attachable to the distal end of said lock shaft toengage and clamp said disc blade against said disc blade mounting platewhen said lock shaft is in its retracted position, and further includesdrive means operatively associated with said mandril and said lock shaftand disposed to reciprocate said lock shaft as aforesaid. 4. A machinefor sharpening disc blades as described in claim 1, in which:

said mandril means includes a mandril having a proxgrinder meansoperatively associated with said frame; 0 said grinder means having agrinding surface disposable in a generally horizontal grinding plane androtatable about an axis, said grinder surface having a configurationsufficient to grind the edges of a disc blade; 15 mandril meansoperatively associated with said frame and said grinder means, saidmandril means includes a mandril housing with a mandril rotatabletherein about an axis, said mandril having a proximal end disposedadjacent said frame and a distal end disposed adjacent said grindingplane, and disc blade mounting means on the distal end of said mandrildisposed to releasably mount a disc blade for engagement by said grindermeans; grinder mounting means mounting said grinder means in said framefor linear movement in alignment with said grinding surface axis and forpivotal movement to swing said grinder means between a work positionwith said grinding surface in said grinding plane and a rest positionwith said grinding surface remote from said grinding plane; and

mandril mounting means mounting said mandril means in said frame withthe axis of said mandril means disposed to form an acute angle with saidgrinding plane, said mandril mounting means having arc adjustment meansoperable to pivot said mandril means about a pivot point disposed alongthe axis thereof to vary said acute angle between said grinding planeand said mandril axis, and axial adjustment means operable to vary theposition of said pivot point along said mandril axis, said mandrilmount-means including a pivotal mounting mounted on said mandril housingadjacent the proximal end of said mandril and supported in said frame,said pivotal mounting being movable axially with respect to said mandrilhousing in alignment with said mandril axis and being movable withrespect to said frame to vary the distance between said point of supportin said frame and said grinding plane.

2. A machine for sharpening disc blades as described in claim 1, inwhich:

said mandril mounting means further includes a trunnioned collarreleasably clamped to said mandril housing adjacent said proximal endand axially movable on said housing for adjustment of said point ofclamping, trunnion bearings on the trunnions of said collar, bearinghousings operatively associated with said trunnion bearings andreleasimal end and a distal end, a housing, a hollow drive shaftrotatably mounted in said housing, a disc blade mounting plate attachedto the distal end of said drive shaft, a lock shaft disposed in the boreof said drive shaft and reciprocally movable with respect thercto froman extended position with the distal end of said lock shaft projectingoutwardly beyond the distal end of said drive shaft to a retractedposition with the distal end of said lock shaft substantiallycoextensive with the distal end of said drive shaft, a clamp platereleasably interlocked with the distal end of said lock shaft anddisposed to engage a disc blade about its center opening and clamp saiddisc blade to said disc blade mounting plate when said lock shaft isreciprocated to its retracted position, lock shaft drive means operatively associated with said drive shaft and mandril housing andactuable to reciprocally drive said lock shaft between said extended andretracted positions, and drive shaft drive means operatively associatedwith said mandril housing and said drive shaft and disposed to rotatesaid drive shaft and a disc blade mounted thereon; and

said axial adjustment means of said mandril mounting means includes atrunnioned collar releasably clamped to said mandril housing adjacentsaid proximal end and axially movable on said housing for adjustment ofsaid point of clamping, trunnion bearings on thetrunnions of saidcollar, bearing housings operatively associated with said trunnionbearings and releasably attachable to said frame, elongated slots insaid frame disposed to receive said trunnions andpermit movement of saidtrunnions in said slots upon release of said attachment of said bearinghousings, all operatively associated to pivotally mount the proximal endof said mandril to said frame; and

said arc adjustment means of said mandril mounting means furtherincludes a mandril slot operatively associated with the. distal en'd ofsaid mandril in cludinga mandril slot operatively associated with saidmandril housing and disposed substantially parallel to the axis of said.mandril, a slot Opera 5 tively associated with said frame and disposedsubstantially parallel to an arcuate path described by the distal end ofsaid mandriluponipivotal movement about said point of pivot mounting ofsaid said grinder means includes a grinder means mounting'arminterconnected with said frame and pivotally movable withrespectathereto to movesaid grinding surface from saidgrinding planeposition 7 and extending axially and radiallyinwardly, a re- I tainerring juxtaposed the face 'surfaceof said cav-- juxtaposed theperipheraledge of a disc blade mounted on said mandril to "a shut downposition. with said grinding surface removed from juxtaposi tion withsaid disc blade peripheral edge, a grinder means mounting plate movablymounted on said grinder means mounting arm for adjustmentof theproximity of said grinding surface to said disc blade peripheral edge,and feed. control means ,operatively associated with said grinder meansmounting 7 arm and said frame and disposedto control the rate of pivotalmovement of said arm with respect to 7 said frame whensaid grindingsurface is juxtaposed 7 said disc blade peripheral edge. e

.6. A machine for sharpening disc bladesas described A in claim 1, whichfurther includes: 7 V

a liquid reservoir disposed to submerge a disc blade;

mounted on the distal end of said mandril.

7.'A machine for sharpening'disc blades as described in'claim l, inwhich:

said grinder mounting means in ,ludes feed means periphery of a discblade mounted on said mandril means at a controlled rate. I

in claim 6, in which:

said liquid reservoir includes a liquid tank operatively' A associatedwith said frameand disposed to receive 8. A machine for sharpening discblades as described 1 a'disc blade mounted on said mandril means, andliquid supply means interconnected with said liquid I tank and disposedto supplyliquid thereto to a level sufficient to submergesubstantiallyall of said discblade.

9 A machine for sharpeningdisc bladesas described in'claim 6, in which:c

said liquid reservoir'includes'a liquid tank operatively associated withsaid frame and disposed to receive a disc blade mounted on said mandrilmeans with" a portion of said mandrilmeans projecting through V a wallof said liquid tank and movable with respect to said Wall, a liquid sealinterconnected between A withsaid liquid tank and'said liquid supplymeans anddisposed to regulate the level of liquidin said liquid tanlcandan auxiliaryliquid conduit opera disposed to move'said grinder meansagainst the .1 grinding surface. s I w h h 1 3,. A machine forsharpening disc blades comprising; a frame; a a A allyhorizontalgrinding plane;

. tivelyassociatedwith saidliquidsupplymeansand saidliquidtankand'disposed tosupply'a streamiof liquid to the pointof contactubetweensaidgrinding: j

surface and said disc blade peripheral edge.

10; A machine for sharpening disc. blades as. de -d I 7 scribed inclaiml, inwhich: s I V a j 1 g saidgrinder means includes grinderdrive means,a

11. A machine for sharpening disc blades as de- ,A AA scribed in claim10, in whichi A saidigrinder chuck releasable clamping means in eludesan annular facesurface surrounding said cavityand disposed substantiallynormalstoi the.

wall's' of said cavity' and a beveled surface inter- 1 posed betweensaid cavity wallsof said face surface.

ity with a beveled surface on itsiinner face extend I ingaxiallyinwardly'and radially outwardly, said retainer ring havingadjustable, securing means disf A posed to tighten and loosen saidretainer 1 ring againstsaid chuck faceisurface, and asplit ring disposedabout the peripheryofsaid cavity and having I- an inner facedisposed toengagesaid grinding 1 A stone and a wedge on its outer face havingtapered l A surfaces disposed forengagement by said'beveledg surfaces onsaid chuck and retainer ring to force' A said split ing radiallyinwardly against theperiph} 1 ery ofsaid grinding stone upon tightening.ofisa idA 1 retainer ring against said chuck face surface.

12.'A machine forjsharpening discblades as'de- A scribed in claim'iinwhichi J i said grinder meansincludes grinder drivemeans, a Igrinderchuckdrivingly interconnected with said I grinder drive means andhaving a circular cavity A and releasable clamping means'and a circular.AA

grinding stone secured in said chuck cavity by said releasable clampingmeanswithan exposedplanarq grinder means operatively associated withsaidframe and having a grindingsurface disposable in agen'en A grindermounting means interconnected withwsaid 7 frame and said grinder meansand disposed to movably mount said grinder meansonsaid frame; g

a rnandril ope'rativelyassociated with said frameand 7 saidgrinder meansand axially disposed in acute I angular relationship with said grindingplane, said mandril having an upper end disposed adjacent saidgrin'dermeans and alower'end'disposed below A said upper end; and juxtaposedsaid frame, said a mandril having a disc blade mountingmeans disposed tomount a disc blade on the upper end. A

thereof; A V .A V A mandril mounting meansinterconnected with said frameand said mandril and having a pivotal mount V ing'adjacent the lower endof sai'dmandril and disa posed to permit arcuate movement" of the upperend of said mandril to change the angular relation T I ship: betweensaid mandril and said grinding sur:

face, and said pivotal mounting being axially movable with respect tosaid mandril'to change the radius of said arcuate movement; and

a liquid containing tank operatively associated with said frame, mandriland grinding surface, and disposed about the upper end of said mandrilfor sub-' mersion of substantially all of a disc blade mounted on saidmandril.

14. A machine for sharpening disc blades as deand said lock shaft andactuatable to axially reciprocate said lock shaft from an extendedposition with the upper end of said lock shaft projecting up- 18. Amachine for sharpening disc blades as de- 5 scribed in claim 13, inwhich:

said grinder mounting means includes a grinder means mounting arminterconnected with said frame and pivotally movable with respectthereto to move said grinding surface from a grinding posiscribed inclaim 13, in which: tion juxtaposed the peripheral edge of a disc bladesaid grinder means includes a drive motor having a I mounted on saidmandril to a shut down position drive shaft interconnected therewith,and a grind-. with said grinding surface removed from juxtaposiing wheelmounted on said shaft and having a tion with said disc blade peripheraledge, a grinder grinding stone and a chuck disposed to releasablymeans-mounting plate movably mounted on said mount said grinding stone;and grinder means mounting arm for adjustment of the said grindermounting means includes feed control proximity of said grinding surfaceto said disc blade means having a hydraulic ram interposed betweenperipheral edge, and feed control means operasaid grinder means and saidframe and intercontively associated with said grinder means mountingnected with variable valve means disposed to reguarm and said frame anddisposed to control the rate late the speed of travel of said ram. 30 ofpivotal movement of said arm with respect to 15. A machine forsharpening disc blades as dei said frame when said grinding surface isjuxtaposed scribed in claim 13, in which: said disc blade peripheraledge; and

said mandril includes a housing and a hollow drive said mandril mountingmeans includes said pivotal shaft rotatably mounted in said housing, andsaid mounting being pivotal for arcuate movement of disc blade mountingmeans includes a disc blade said distal end of said mandril with respectto said mounting plate affixed to the upper end of said proximal end,and being releasably securedto said drive shaft inside said tank, a lockshaft disposed in mandril for axial adjustment with respect thereto tothe bore of said hollow drive shaft, lock shaft drive vary the distancebetween said pivotal mounting means interconnected with said mandrilhousing andsaid mandril'distal end. and beingadjustably mounted to saidframe for movement of said point of mounting toward and away from saidgrinder means.

wardly beyond said disc blade mounting plate to a retracted positionwith the upper end of saidlock shaft substantially co-extensive withsaid disc blade 19. A, machine for sharpening disc blades as describedinclaim '13, in which:

said mandril mounting means includes a trunnioned mounting plate whensaid lock shaft is reciprocated to its retracted position.

collar releasably clamped to said mandril housing adjacent said proximalend and axially movable on said housing for adjustment of said point ofclamping. trunnion hearings on the trunnions of said collar, bearinghousings operatively associated with said trunnion bearings andreleasably attachable to said frame. elongated slots in said framedisposed 16. A machine for sharpening disc blades as deto receive saidtrunnions and permit movement of scribed in claim 13 in which:

said pivotal mounting of said mandril mounting I tachment of saidbearing housingsall'operatively said trunnions in said slots upon.releaserofsaid atof mounting toward and away from said grinder,

means.

tank and disposed to supply liquid to said liquid tank to a levelsufficient to submerge substantially all of said disc blade, levelcontrol means operatively associated with said liquid tank and saidliqassociated to pivotally mount the proximal end of said mandril tosaid frame; and

said mandril mounting means further includes arc positioning meansoperatively associated with the distal end of said mandril including amandril slot operatively associated with the distal end of said mandrilincluding a mandril slot operatively associated with said mandrilhousing and disposed substantially parallel to the axis of said mandril,,a slot op- 17. A machine for sharpening disc blades as deerativelyassociated with said frame and disposed scribed in claim 13 in which:substantially parallel. to an arcuate path described said liquidcontaining tank includes a liquid seal inby the distal end of saidmandril upon pivotal terconnected betweensaid wall and said mandril,movement aboutsaid point of pivot mounting of liquid supply meansinterconnected with said liquid said mandril. and lock bolt meansdisposed in said mandril slot and frame slot and releasably lockable tosecure said distal end of said mandril to said frame at a predeterminedposition along said arcuate path. I

20. A machine for sharpening disc blades as described in claim 15, inwhich:

said mandril mounting means includes a trunnioned collar releasablyclamped to said mandril housing uid supply means and disposed toregulate the level of liquid in said liquid tank, and an auxiliaryliquid conduit operatively associated with said liquid supply means andsaid liquid tank and disposed to sup- V adjzicent saidlproximal end andaxially: movable on said housing for adjustment of said point of clampeing, trunnion bearings on the trunnions of said cob lar, bearinghousings operatively associatedrwith o said trunnion bearingsandreleasablyattachcd to said frame, elongated slots insaidifr amedispqsedito receive said trunnions and permit movement of associated to pivotallymount the proximal end of said mandrilto said frame; and V V 7 saidma'ndril mounting means further includes arc po- '7 V sitioning meansoperatively associatedrwith the dis- I tail end of said inandrilincluding amandrilsl ot op f I I f l I eratiiiely associated with" saidmz indriihousing and i i disposed substantially parallelit'ofthe' axisofsaid -mdndril *a frame -slot roperatively i associated with f said frameand disposed substantially parallel to anf V rarc uate path described bytherdistalend {of said {mandril upon pivotal moy'ementabout said pointof W pivot mount'ingxofsaid,mandrilQpand lock bolt 1 means disposed'insaidmiindril slot and frame slot and releasably lockztblel to securesaid distal 'end of said mandril to said frame ata, predeterminedposition alongsaidarcu ate path. v i V 1

1. A machine for sharpening disc blades comprising: a frame; grindermeans operatively associated with said frame; said grinder means havinga grinding surface disposable in a generally horizontal grinding planeand rotatable about an axis, said grinder surface having a configurationsufficient to grind the edges of a disc blade; mandril means operativelyassociated with said frame and said grinder means, said mandril meansincludes a mandril housing with a mandril rotatable therein about anaxis, said mandril having a proximal end disposed adjacent said frameand a distal end disposed adjacent said grinding plane, and disc blademounting means on the distal end of said mandril disposed to releasablymount a disc blade for engagement by said grinder means; grindermounting means mounting said grinder means in said frame for linearmovement in alignment with said grinding surface axis and for pivotalmovement to swing said grinder means between a work position with saidgrinding surface in said grinding plane and a rest position with saidgrinding surface remote from said grinding plane; and mandril mountingmeans mounting said mandril means in said frame with the axis of saidmandril means disposed to form an acute angle with said grinding plane,said mandril mounting means having arc adjustment means operable topivot said mandril means about a pivot point disposed along the axisthereof to vary said acute angle between said grinding plane and saidmandril axis, and axial adjustment means operable to vary the positionof said pivot point along said mandril axis, said mandril mount-meansincluding a pivotal mounting mounted on said mandril housing adjacentthe proximal end of said mandril and supported in said frame, saidpivotal mounting being movable axially with respect to said mandrilhousing in alignment with said mandril axis and being movable withrespect to said frame to vary the distance between said point of supportin said frame and said grinding plane.
 2. A machine for sharpening discblades as described in claim 1, in which: said mandril mounting meansfurther includes a trunnioned collar releasably clamped to said mandrilhousing adjacent said proximal end and axially movable on said housIngfor adjustment of said point of clamping, trunnion bearings on thetrunnions of said collar, bearing housings operatively associated withsaid trunnion bearings and releasably attachable to said frame,elongated slots in said frame disposed to receive said trunnions andpermit movement of said trunnions in said slots upon release of saidattachment of said bearing housings, all operatively associated topivotally mount the proximal end of said mandril to said frame.
 3. Amachine for sharpening disc blades as described in claim 1, in which:said mandril means includes a mandril having a proximal end mounted tosaid frame and a distal end disposed adjacent said grinding surface withdisc blade clamp means thereon, said disc blade clamp means having alock shaft interconnected with said mandril with a proximal end adjacentthe proximal end of said mandril and a distal end adjacent the distalend of said mandril and disposed for reciprocating axial movement withrespect to said mandril from an extended position with said distal endof said lock shaft extended outwardly from the distal end of saidmandril to a retracted position with the distal end of said lock shaftsubstantially coextensive with the distal end of said mandril, andhaving a disc blade mounting plate on the distal end of said mandril,and further includes a lock plate releasably attachable to the distalend of said lock shaft to engage and clamp said disc blade against saiddisc blade mounting plate when said lock shaft is in its retractedposition, and further includes drive means operatively associated withsaid mandril and said lock shaft and disposed to reciprocate said lockshaft as aforesaid.
 4. A machine for sharpening disc blades as describedin claim 1, in which: said mandril means includes a mandril having aproximal end and a distal end, a housing, a hollow drive shaft rotatablymounted in said housing, a disc blade mounting plate attached to thedistal end of said drive shaft, a lock shaft disposed in the bore ofsaid drive shaft and reciprocally movable with respect thereto from anextended position with the distal end of said lock shaft projectingoutwardly beyond the distal end of said drive shaft to a retractedposition with the distal end of said lock shaft substantiallycoextensive with the distal end of said drive shaft, a clamp platereleasably interlocked with the distal end of said lock shaft anddisposed to engage a disc blade about its center opening and clamp saiddisc blade to said disc blade mounting plate when said lock shaft isreciprocated to its retracted position, lock shaft drive meansoperatively associated with said drive shaft and mandril housing andactuable to reciprocally drive said lock shaft between said extended andretracted positions, and drive shaft drive means operatively associatedwith said mandril housing and said drive shaft and disposed to rotatesaid drive shaft and a disc blade mounted thereon; and said axialadjustment means of said mandril mounting means includes a trunnionedcollar releasably clamped to said mandril housing adjacent said proximalend and axially movable on said housing for adjustment of said point ofclamping, trunnion bearings on the trunnions of said collar, bearinghousings operatively associated with said trunnion bearings andreleasably attachable to said frame, elongated slots in said framedisposed to receive said trunnions and permit movement of said trunnionsin said slots upon release of said attachment of said bearing housings,all operatively associated to pivotally mount the proximal end of saidmandril to said frame; and said arc adjustment means of said mandrilmounting means further includes a mandril slot operatively associatedwith the distal end of said mandril including a mandril slot operativelyassociated with said mandril housing and disposed substantially parallelto the axis of said mandril, a slot operatively associated with saidframe and disposed substantially parallel to an arcuAte path describedby the distal end of said mandril upon pivotal movement about said pointof pivot mounting of said mandril, and lock bolt means disposed in saidmandril slot and frame slot and releasably lockable to secure saiddistal end of said mandril to said frame at a predetermined positionalong said arcuate path.
 5. A machine for sharpening disc blades asdescribed in claim 4, in which: said grinder means includes a grindermeans mounting arm interconnected with said frame and pivotally movablewith respect thereto to move said grinding surface from said grindingplane position juxtaposed the peripheral edge of a disc blade mounted onsaid mandril to a shut down position with said grinding surface removedfrom juxtaposition with said disc blade peripheral edge, a grinder meansmounting plate movably mounted on said grinder means mounting arm foradjustment of the proximity of said grinding surface to said disc bladeperipheral edge, and feed control means operatively associated with saidgrinder means mounting arm and said frame and disposed to control therate of pivotal movement of said arm with respect to said frame whensaid grinding surface is juxtaposed said disc blade peripheral edge. 6.A machine for sharpening disc blades as described in claim 1, whichfurther includes: a liquid reservoir disposed to submerge a disc blademounted on the distal end of said mandril.
 7. A machine for sharpeningdisc blades as described in claim 1, in which: said grinder mountingmeans includes feed means disposed to move said grinder means againstthe periphery of a disc blade mounted on said mandril means at acontrolled rate.
 8. A machine for sharpening disc blades as described inclaim 6, in which: said liquid reservoir includes a liquid tankoperatively associated with said frame and disposed to receive a discblade mounted on said mandril means, and liquid supply meansinterconnected with said liquid tank and disposed to supply liquidthereto to a level sufficient to submerge substantially all of said discblade.
 9. A machine for sharpening disc blades as described in claim 6,in which: said liquid reservoir includes a liquid tank operativelyassociated with said frame and disposed to receive a disc blade mountedon said mandril means with a portion of said mandril means projectingthrough a wall of said liquid tank and movable with respect to saidwall, a liquid seal interconnected between said wall and said mandrilmeans, liquid supply means interconnected with said liquid tank anddisposed to supply liquid to said liquid tank to a level sufficient tosubmerge substantially all of said disc blade, level control meansoperatively associated with said liquid tank and said liquid supplymeans and disposed to regulate the level of liquid in said liquid tank,and an auxiliary liquid conduit operatively associated with said liquidsupply means and said liquid tank and disposed to supply a stream ofliquid to the point of contact between said grinding surface and saiddisc blade peripheral edge.
 10. A machine for sharpening disc blades asdescribed in claim 1, in which: said grinder means includes grinderdrive means, a grinder chuck drivingly interconnected with said grinderdrive means and having a circular cavity and releasable clamping meansand a circular grinding stone secured in said chuck cavity by saidreleasable clamping means with an exposed planar grinding surface.
 11. Amachine for sharpening disc blades as described in claim 10, in which:said grinder chuck releasable clamping means includes an annular facesurface surrounding said cavity and disposed substantially normal to thewalls of said cavity, and a beveled surface interposed between saidcavity walls of said face surface and extending axially and radiallyinwardly, a retainer ring juxtaposed the face surface of said cavitywith a beveled surface on its inner face extending axially inwardly andradially outwardly, said retainer ring havIng adjustable securing meansdisposed to tighten and loosen said retainer ring against said chuckface surface, and a split ring disposed about the periphery of saidcavity and having an inner face disposed to engage said grinding stoneand a wedge on its outer face having tapered surfaces disposed forengagement by said beveled surfaces on said chuck and retainer ring toforce said split ring radially inwardly against the periphery of saidgrinding stone upon tightening of said retainer ring against said chuckface surface.
 12. A machine for sharpening disc blades as described inclaim 5, in which: said grinder means includes grinder drive means, agrinder chuck drivingly interconnected with said grinder drive means andhaving a circular cavity and releasable clamping means and a circulargrinding stone secured in said chuck cavity by said releasable clampingmeans with an exposed planar grinding surface.
 13. A machine forsharpening disc blades comprising: a frame; grinder means operativelyassociated with said frame and having a grinding surface disposable in agenerally horizontal grinding plane; grinder mounting meansinterconnected with said frame and said grinder means and disposed tomovably mount said grinder means on said frame; a mandril operativelyassociated with said frame and said grinder means and axially disposedin acute angular relationship with said grinding plane, said mandrilhaving an upper end disposed adjacent said grinder means and a lower enddisposed below said upper end and juxtaposed said frame, said mandrilhaving a disc blade mounting means disposed to mount a disc blade on theupper end thereof; mandril mounting means interconnected with said frameand said mandril and having a pivotal mounting adjacent the lower end ofsaid mandril and disposed to permit arcuate movement of the upper end ofsaid mandril to change the angular relationship between said mandril andsaid grinding surface, and said pivotal mounting being axially movablewith respect to said mandril to change the radius of said arcuatemovement; and a liquid containing tank operatively associated with saidframe, mandril and grinding surface, and disposed about the upper end ofsaid mandril for submersion of substantially all of a disc blade mountedon said mandril.
 14. A machine for sharpening disc blades as describedin claim 13, in which: said grinder means includes a drive motor havinga drive shaft interconnected therewith, and a grinding wheel mounted onsaid shaft and having a grinding stone and a chuck disposed toreleasably mount said grinding stone; and said grinder mounting meansincludes feed control means having a hydraulic ram interposed betweensaid grinder means and said frame and interconnected with variable valvemeans disposed to regulate the speed of travel of said ram.
 15. Amachine for sharpening disc blades as described in claim 13, in which:said mandril includes a housing and a hollow drive shaft rotatablymounted in said housing, and said disc blade mounting means includes adisc blade mounting plate affixed to the upper end of said drive shaftinside said tank, a lock shaft disposed in the bore of said hollow driveshaft, lock shaft drive means interconnected with said mandril housingand said lock shaft and actuatable to axially reciprocate said lockshaft from an extended position with the upper end of said lock shaftprojecting upwardly beyond said disc blade mounting plate to a retractedposition with the upper end of said lock shaft substantiallyco-extensive with said disc blade mounting plate, and a clamping platereleasably engagable with the upper end of said lock shaft when saidlock shaft is in its extended position and disposed to engage a discblade about its center opening and clamp said disc blade to said discblade mounting plate when said lock shaft is reciprocated to itsretracted position.
 16. A machine for sharpening disc blades asdescribed in claim 13 iN which: said pivotal mounting of said mandrilmounting means is pivotal for arcuate movement of said distal end ofsaid mandril with respect to said proximal end, and being releasablysecured to said mandril for axial adjustment with respect thereto tovary the distance between said pivotal mounting and said mandril distalend, and being adjustably mounted to said frame for movement of saidpoint of mounting toward and away from said grinder means.
 17. A machinefor sharpening disc blades as described in claim 13 in which: saidliquid containing tank includes a liquid seal interconnected betweensaid wall and said mandril, liquid supply means interconnected with saidliquid tank and disposed to supply liquid to said liquid tank to a levelsufficient to submerge substantially all of said disc blade, levelcontrol means operatively associated with said liquid tank and saidliquid supply means and disposed to regulate the level of liquid in saidliquid tank, and an auxiliary liquid conduit operatively associated withsaid liquid supply means and said liquid tank and disposed to supply astream of liquid to the point of contact between said grinding surfaceand said disc blade peripheral edge.
 18. A machine for sharpening discblades as described in claim 13, in which: said grinder mounting meansincludes a grinder means mounting arm interconnected with said frame andpivotally movable with respect thereto to move said grinding surfacefrom a grinding position juxtaposed the peripheral edge of a disc blademounted on said mandril to a shut down position with said grindingsurface removed from juxtaposition with said disc blade peripheral edge,a grinder means mounting plate movably mounted on said grinder meansmounting arm for adjustment of the proximity of said grinding surface tosaid disc blade peripheral edge, and feed control means operativelyassociated with said grinder means mounting arm and said frame anddisposed to control the rate of pivotal movement of said arm withrespect to said frame when said grinding surface is juxtaposed said discblade peripheral edge; and said mandril mounting means includes saidpivotal mounting being pivotal for arcuate movement of said distal endof said mandril with respect to said proximal end, and being releasablysecured to said mandril for axial adjustment with respect thereto tovary the distance between said pivotal mounting and said mandril distalend, and being adjustably mounted to said frame for movement of saidpoint of mounting toward and away from said grinder means.
 19. A machinefor sharpening disc blades as described in claim 13, in which: saidmandril mounting means includes a trunnioned collar releasably clampedto said mandril housing adjacent said proximal end and axially movableon said housing for adjustment of said point of clamping, trunnionbearings on the trunnions of said collar, bearing housings operativelyassociated with said trunnion bearings and releasably attachable to saidframe, elongated slots in said frame disposed to receive said trunnionsand permit movement of said trunnions in said slots upon release of saidattachment of said bearing housings, all operatively associated topivotally mount the proximal end of said mandril to said frame; and saidmandril mounting means further includes arc positioning meansoperatively associated with the distal end of said mandril including amandril slot operatively associated with the distal end of said mandrilincluding a mandril slot operatively associated with said mandrilhousing and disposed substantially parallel to the axis of said mandril,a slot operatively associated with said frame and disposed substantiallyparallel to an arcuate path described by the distal end of said mandrilupon pivotal movement about said point of pivot mounting of saidmandril, and lock bolt means disposed in said mandril slot and frameslot and releasably lockable to secure said distal end of said mandrilto said frame at a predetermined posiTion along said arcuate path.
 20. Amachine for sharpening disc blades as described in claim 15, in which:said mandril mounting means includes a trunnioned collar releasablyclamped to said mandril housing adjacent said proximal end and axiallymovable on said housing for adjustment of said point of clamping,trunnion bearings on the trunnions of said collar, bearing housingsoperatively associated with said trunnion bearings and releasablyattached to said frame, elongated slots in said frame disposed toreceive said trunnions and permit movement of said trunnions in saidslots upon release of said attachment of said bearing housings, alloperatively associated to pivotally mount the proximal end of saidmandril to said frame; and said mandril mounting means further includesarc positioning means operatively associated with the distal end of saidmandril including a mandril slot operatively associated with saidmandril housing and disposed substantially parallel to the axis of saidmandril, a frame slot operatively associated with said frame anddisposed substantially parallel to an arcuate path described by thedistal end of said mandril upon pivotal movement about said point ofpivot mounting of said mandril, and lock bolt means disposed in saidmandril slot and frame slot and releasably lockable to secure saiddistal end of said mandril to said frame at a predetermined positionalong said arcuate path.